Very useful and simple to use. I think I like it better than Chrome's profile switching.

A must have. I've switched all of my multi-profile activity from Chromium (not my preferred browser) to Firefox (my preferred and favorite browser) Multi-Account Containers, finding it much more useful, handy and, especially, resource efficient. Keep it up, Mozilla!

Simply exceptional. This add-on is the one that kept me using Firefox because it is very, very useful. I can have many "profiles" with which to log into the same websites using different accounts. It's super easy to use and works perfectly. The container settings menu (second screenshot) could take some polish, but overall it doesn't hinder the usability of the add-on.

My job as a freelance translator means I work for different clients who sometimes use the same services, i.e., I have more than one account with those services. Without Multi-Account Containers, my job would be a nightmare. Best add-on ever.

Great extension, just needs syncing so we don't have to repeat setup on every device.

Pros: 5 stars because it does what it says it does and well.
Cons: No saving settings across devices.

Almost perfect extension for me. It let me separate accounts on sites or group sites...
After mess-up with certificates I lost all my custom made preferences and containers. Add back up ability even if I move to other computer and login to my Mozilla account I feel same good Firefox I'm used to.

Perfectly addresses the need for being able to be logged in to the same site under two different accounts at the same time.